1. Field of the Invention
This invention relates to reciprocal type pumps or motors and more particularly to linear type actuators which are controlled by solid state electrical circuits.
2. Description of the Prior Art
Rotational motors using bearings, seals, cams and/or linkages for pumping gases or liquids, or for direct drive of such tools as automatic saws, clippers, or linear actuators for control of machinery are well known.
Pumps of this type are described in prior patents such as U.S. Pat. No. 3,437,044 entitled "Fluid cooled double solenoid pumping mechanism", dated Apr. 8, 1969, and U.S. Pat. No. 3,282,219 entitled "Double acting solenoid pump", dated Nov. 1, 1966. Pumps of this type are described in these patents and are driven by a relay which alternately energizes two coils. Relays operate much too slowly and have too short a life expectancy to make these pumps practical. Other reciprocating plunger type pumps presently on the market such as automotive fuel pumps and refrigeration pumps use a single coil to move the plunger in one direction and a spring to return the plunger to its initial position. The springs are subject to fatigue failure and cannot be controlled to provide variable pressure or flow. Reciprocating motion for machinery tools is accomplished by a rotating motor with various types of cams and linkages to convert rotary motion to linear motion. These devices are usually driven by a universal motor which has carbon brushes and a commutator. Life is shortened due to brush wear and mechanical linkage failure. The cost of components adds substantially to the manufacturing cost of devices of the type described above. Solenoids used for machine actuation are also generally of the spring return type and must be actuated from a separate clock, counter, or relay closure.